Device, network, and method for csi feedback of hybrid beamforming

ABSTRACT

Various methods and systems are provided to provide for Channel State Information (CSI) feedback of hybrid beamforming. In a first example embodiment, a method for signaling a beamforming reference signal (BFRS) is provided. A resource block is created for the BFRS, the resource block containing a plurality of resource elements, each resource element defined by a time-frequency resource within one subcarrier and one multiplexing symbol. A total number of analog transmit beams for the BFRS is then determined, along with grouping information for the analog transmit beams for the BFRS. Then, the resource block, the total number of analog beams, and the grouping information are transmitted from a first network controller to a user equipment (UE). Then the BFRS is transmitted from the first network controller to the UE.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/139,674, filed on Apr. 27, 2016, which claims the benefit of priorityof U.S. Provisional Patent Application Ser. No. 62/155,818, filed on May1, 2015. All of the aforementioned patent applications are herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a device, network, and method forwireless communications, and, in particular embodiments, to a device andmethod for Channel State Information (CSI) feedback of hybrid antennabeamforming.

BACKGROUND

The amount of wireless data utilized in mobile networks has increaseddramatically in the last few years, pushing the capacity of currentmacro cellular deployments. Cellular communications systems, whichutilize microwave spectrum bands (300 MHz to 3 GHz), are becomingcapacity-limited due to interference and traffic load. The use of highfrequency bands, where vast amounts of bandwidth is available, isconsidered to be a crucial technology for future generationcommunication systems. The use of these frequency bands (e.g., 28, 38,60 and 73 GHz) can mitigate the problem of capacity currently observed.

Propagation in the millimeter band (mmWave) is much more challengingthan in the microwave band, resulting in a more stringent link budget ata mmWave band than at a microwave band. Equipping both the transmitterand receiver with a larger number of antenna arrays is a viable solutionto compensate for the mmWave extra path loss by beamforming.

Since antenna size is inversely proportional to the carrier frequency,the use of these high frequency bands reduces the antenna sizeconsiderably. This opens the door to employ a larger number of transmitand receive antenna arrays at both network and terminal sides.

Hybrid antenna architecture may be used to trade off hardwarecomplexity, power consumption, and the performance and coverage of thesystem. Hybrid antenna architecture typically includes analog (phaseshifter) and digital (baseband pre-coder) beamforming parts.

A base station may include one or more Radio Frequency (RF) chains, andeach RF chain is connected to analog phase shifters and antenna arrays.A user equipment (UE) receiver may include one or more RF chainsconnected to receiver analog phase shifters and antenna arrays.

There are different types of analog beamforming architectures. Two sucharchitectures are shared array and sub-array.

SUMMARY

Various methods and systems are provided to provide for channel stateinformation (CSI) feedback of hybrid beamforming. In a first exampleembodiment, a method for signaling a beamforming reference signal (BFRS)is provided. A resource block is created for the BFRS, the resourceblock containing a plurality of resource elements, each resource elementdefined by a time-frequency resource within one subcarrier and onemultiplexing symbol. A total number of analog transmit beams for theBFRS is then determined, along with grouping information for the analogtransmit beams for the BFRS. Then, the resource block, the total numberof analog beams, and the grouping information are transmitted from afirst network controller to a user equipment (UE). Then the BFRS istransmitted from the first network controller to the UE.

In a second example embodiment, a method for utilizing a beamformingreference signal (BFRS) is provided. A resource block for the BFRS isreceived at a UE, along with a total number of analog beams for theBFRS, and grouping information for the BFRS, the resource blockcontaining a plurality of resource elements, each resource elementdefined by a time-frequency resource within one subcarrier and onemultiplexing symbol. Then a BFRS is received by the UE. Beam pairselection is performed to form effective multiple-input andmultiple-output (MIMO) channels using the resource block, the totalnumber of analog beams, and the grouping information by selecting one ormore best transmit-receive beam pairs, while limiting each effectiveMIMO channel to including a single transmit analog beam per beam group.Then the UE derives, based on the effective MIMO channels, acorresponding CSI feedback. At least one set of recommendations of achannel for each supported rank by the BFRS is calculated based on theCSI feedback, each supported rank corresponding to a different stream ofsymbols transmitted in the BFRS. Then the at least one set ofrecommendations is reported.

In a third example embodiment, another method for utilizing abeamforming reference signal (BFRS) is provided. A resource block forthe BFRS is received at the UE, along with a total number of analogbeams for the BFRS and grouping information for the BFRS, the resourceblock containing a plurality of resource elements, each resource elementdefined by a time-frequency resource within one subcarrier and onemultiplexing symbol. Then a BFRS is received by the UE. Beam pairselection is performed to form effective MIMO channels using theresource block, the total number of analog beams, and the groupinginformation by selecting one or more best transmit-receive beam pairs,while limiting each effective MIMO channel to including a singletransmit analog beam per beam group. The UE then transmits to thenetwork controller a report of indexes of the selected besttransmit-receive beam pairs. Then the UE transmits to the networkcontroller an uplink sounding signal by applying the selected besttransmit-receive beam pairs.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present inventive subjectmatter, and the benefits thereof, reference is now made to the followingdescriptions taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 shows an example of one hybrid beamforming architecture with ashared array.

FIG. 2 shows an example of another hybrid beamforming architecture witha sub-array.

FIG. 3 depicts how the transmission/reception from controller to a UE iscalled downlink (DL) transmission/reception, and thetransmission/reception from a UE to a controller is called uplink (UL)transmission/reception.

FIG. 4 is an interaction diagram illustrating a method of handshakingbetween an evolved NodeB (eNB) and an UE in accordance with an exampleembodiment.

FIG. 5 is an interaction diagram illustrating another method ofhandshaking between an eNB and an UE in accordance with another exampleembodiment.

FIG. 6 is a diagram illustrating an example resource block in accordancewith an example embodiment.

FIG. 7 is a diagram showing example data packets in accordance with anexample embodiment.

FIG. 8 is a diagram illustrating an example frame structure inaccordance with an example embodiment.

FIG. 9 is a diagram illustrating a system for sequentially transmittinga beam scanning signal in accordance with an example embodiment.

FIG. 10 is a block diagram illustrating a representative softwarearchitecture, which may be used in conjunction with various hardwarearchitectures herein described.

FIG. 11 is a block diagram illustrating components of a machine,according to some example embodiments, able to read instructions from amachine-readable medium (e.g., a machine-readable storage medium) andperform any one or more of the methodologies discussed herein.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings, which form a part hereof, and in which are shown, by way ofillustration, specific embodiments which may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the subject matter disclosed herein, and it is tobe understood that other embodiments may be utilized and thatstructural, logical, and electrical changes may be made withoutdeparting from the scope of the present disclosure. The followingdescription of example embodiments is, therefore, not to be taken in alimiting sense, and the scope of the present disclosure is defined bythe appended claims.

The functions or algorithms described herein may be implemented insoftware or a combination of software and human-implemented proceduresin one embodiment. The software may consist of computer-executableinstructions stored on computer-readable media or a computer-readablestorage device such as one or more non-transitory memories or othertypes of hardware-based storage devices, either local or networked.Further, such functions correspond to modules, which may be software,hardware, firmware, or any combination thereof. Multiple functions maybe performed in one or more modules as desired, and the embodimentsdescribed are merely examples. The software may be executed on a digitalsignal processor, application-specific integrated circuit (ASIC),microprocessor, or other type of processor operating on a computersystem, such as a personal computer, server, or other computer system.

In a modern wireless communications system, such as a Third GenerationPartnership Project (3GPP) Long Term Evolution (LTE) compliantcommunications system, a plurality of cells or evolved NodeBs (eNB)(also commonly referred to as NodeBs, base stations (BSs), base terminalstations, communications controllers, network controllers, controllers,access points (APs), and so on) may be arranged into a cluster of cells,with each cell having multiple transmit antennas. Additionally, eachcell or eNB may be serving a number of users (also commonly referred toas User Equipment (UE), mobile stations, users, subscribers, terminals,and so forth) based on a priority metric, such as fairness, proportionalfairness, round robin, and the like, over a period of time. It is notedthat the terms cell, transmission points, and eNB may be usedinterchangeably. Distinction between cells, transmission points, andeNBs will be made where needed.

FIG. 1 shows an example of one hybrid beamforming architecture 100 witha shared array. The architecture 100 includes a baseband beamformingtransmitter 102 and a baseband beamforming receiver 104. In one exampleembodiment the baseband beamforming transmitter 102 may be implementedas a baseband beamforming transmission means. In another exampleembodiment, the baseband beamforming receiver 104 may be implemented asa baseband beamforming receiving means. The baseband beamformingtransmitter 102 includes a plurality of precoders 106A-106B. Theprecoders 106A-106B act to exploit transmit diversity by weightinginformation streams. In an example embodiment, each of the precoders106A-106B may be implemented as a precoding means. Digital-to-Analogconverters (DACs) 108A, 108B then act to convert the precoded digitalsignals to analog signals to send to the transmitter shared array 110.In an example embodiment, each of the DACs 108A, 108B may be implementedas a digital-to-analog conversion means. In another example embodiment,the transmitter shared array 110 may be implemented as a transmittershared array means. A receiver shared array 112 then receives thetransmitted signal, and one or more analog-to-digital converters (ADCs)114A, 114B convert the received signal to digital. In an exampleembodiment, the receiver shared array 112 may be implemented as areceiver shared array means. In another example embodiment, each of theADCs 114A, 114B may be implemented as an analog-to-digital conversionmeans. Finally, one or more equalizers 116A, 116B to equalize thedigital signals. In an example embodiment, each of the equalizers 116A,116B may be implemented as an equalization means.

FIG. 2 shows an example of another hybrid beamforming architecture 200with a sub-array. This architecture 200 provides a lower complexityversion of the hybrid beamforming architecture 100 of FIG. 1 by reducingthe number of phase shifters and omitting the need for RF combiners onthe transmission side. However, the rest of the architecture 200 is thesame as the shared hybrid beamforming architecture 100 of FIG. 1. Thearchitecture 200 includes a baseband beamforming transmitter 202 and abaseband beamforming receiver 204. In one example embodiment thebaseband beamforming transmitter 202 may be implemented as a basebandbeamforming transmission means. In another example embodiment, thebaseband beamforming receiver 204 may be implemented as a basebandbeamforming receiving means. The baseband beamforming transmitter 202includes a plurality of precoders 206A-206B. The precoders 206A-206B actto exploit transmit diversity by weighting information streams. In anexample embodiment, each of the precoders 206A-206B may be implementedas a precoding means. Digital-to-Analog converters (DACs) 208A, 208Bthen act to convert the precoded digital signals to analog signals tosend to the transmitter sub-array 210. In an example embodiment, each ofthe DACs 208A, 208B may be implemented as a digital-to-analog conversionmeans. In another example embodiment, the transmitter sub-array 210 maybe implemented as a transmitter shared array means. A receiver sub-array212 then receives the transmitted signal, and one or moreanalog-to-digital converters (ADCs) 214A, 214B convert the receivedsignal to digital. In an example embodiment, the receiver sub-array 212may be implemented as a receiver sub-array means. In another exampleembodiment, each of the ADCs 214A, 214B may be implemented as ananalog-to-digital conversion means. Finally, one or more equalizers216A, 216B equalize the digital signals. In an example embodiment, eachof the equalizers 216A, 216B may be implemented as an equalizationmeans.

FIG. 3 depicts how the transmission/reception from controller 300 to aUE 302 is called downlink (DL) transmission/reception, and thetransmission/reception from a UE 304 to a controller 300 is calleduplink (UL) transmission/reception.

FIG. 4 is an interaction diagram illustrating a method 400 ofhandshaking between an eNb 402 and a UE 404 in accordance with anexample embodiment. Here, at operation 406, the eNb 402 signals beamscanning transmission information and restriction configurations to theUE 404. This may be performed by creating a resource block for the BFRS,the resource block containing a plurality of resource elements, eachresource element defined by a time-frequency resource within onesubcarrier and one multiplexing symbol, determining a total number ofanalog transmit beams for the BFRS, and determining grouping informationfor the analog transmit beams for the BFRS and then transmitting thisinformation to the UE 404. The resource blocks include time andfrequency at which the BFRS is transmitted, and a sequence to generatethe BFRS. This may also include determining a set of analog beamselection restriction configurations, the analog beam selectionrestriction configurations indicating a set of analog beams upon whichthe UE should not derive a digital Channel State Information (CSI)feedback, and transmitting this information to the UE 404.

Then, at operation 408, the eNb 402 transmits the beam scanningreference signal to the UE 404. At operation 410, the UE 404 selects thebest transmit-receive analog beam pairs with restrictions. The beamscanning reference signal may be a combination of wide beams and narrowbeams. To derive a digital effective channel, the UE 404 can berestricted not to use any of the wide beams. At operation 412, the UE404 forms effective MIMO channels and virtual antenna ports using theresource block, the total number of analog beams, and the groupinginformation, while limiting each effective MIMO channel to including asingle transmit analog beam per beam group. At operation 414, the UE 404derives baseband CSI feedback based on the digital MIMO channels. Atoperation 416, the UE 404 compiles both analog and digital CSI reports.This may include calculating at least one set of recommendations of achannel for each supported rank by the BFR based on the CSI feedback,each supported rank corresponding to a different stream of symbolstransmitted in the BFRS. Then, at operation 418, the UE 404 sends hybridCSI reports (from the analog and digital CSI reports) to the eNb 402.

FIG. 5 is an interaction diagram illustrating another method 500 ofhandshaking between an eNb 502 and a UE 504 in accordance with anotherexample embodiment. Here, at operation 506, the eNb 502 signals beamscanning transmission information and restriction configurations to theUE 504. This may be performed by creating a resource block for the BFRS,the resource block containing a plurality of resource elements, eachresource element defined by a time-frequency resource within onesubcarrier and one multiplexing symbol, determining a total number ofanalog transmit beams for the BFRS, and determining grouping informationfor the analog transmit beams for the BFRS, and then transmitting thisinformation to the UE 504. The resource blocks include time andfrequency at which the BFRS is transmitted, and a sequence to generatethe BFRS. This may also include determining a set of analog beamselection restriction configurations, the analog beam selectionrestriction configurations indicating a set of analog beams upon whichthe UE should not derive a digital Channel State Information (CSI)feedback, and transmitting this information to the UE 504.

Then, at operation 508, the eNb 502 transmits the beam scanningreference signal to the UE 504. At operation 510, the UE 404 selects thebest transmit-receive analog beam pairs with restrictions. The beamscanning reference signal may be a combination of wide beams and narrowbeams. To derive a digital effective channel, the UE 504 can berestricted not to use any of the wide beams. At operation 512, the UE504 reports the best transmit beam indexes to the eNb 502. At operation514, the UE 504 sends an uplink sounding signal to the eNb 502 byapplying the receive beams. At operation 516, the eNb 502 receives thesignal using the reported transmit beams as receive beams. At operation518, the baseband CSI is derived for data transmissions.

In Orthogonal frequency-division multiplexing (OFDM) systems, thefrequency bandwidth is divided into multiple subcarriers in thefrequency domain. In the time domain, one subframe is divided intomultiple OFDM symbols. The OFDM symbol may have a cyclic prefix to avoidinter-symbol interference due to multiple path delays. One resourceelement (RE) is defined by the time-frequency resource within onesubcarrier and one OFDM symbol. A reference signal and other signals,such as data channel, e.g. physical downlink shared channel (PDSCH), andcontrol channel, e.g. physical downlink control channel (PDCCH), areorthogonal and multiplexed in different resource elements in thetime-frequency domain. Further, the signals are modulated and mappedinto resource elements. Using inverse Fourier transform per each OFDMsymbol, the signals in the frequency domain are transformed into thesignals in the time domain, and are transmitted with an added cyclicprefix to avoid the inter-symbol interference.

Each resource block (RB) contains a number of REs. FIG. 6 is a diagramillustrating an example resource block 600 in accordance with an exampleembodiment. The resource block 600 comprises a number of differentresource elements, such as resource element 602. For each resource block600, there are 14 OFDM symbols labeled from 0 to 13 in each subframe.The symbols 0 to 6 in each subframe correspond to even slots, and thesymbols 7 to 13 in each subframe correspond to odd slots. In the figure,only seven OFBM symbols across are shown (604). There are also 12subcarriers (606) in each resource block 600, and hence in this example,there are 84 REs in a RB. In each subframe, there are a number of RBs,and the number may depend on the bandwidth (BW).

FIG. 7 is a diagram showing example data packets 700A, 700B inaccordance with an example embodiment. The data channels transmittingdata packets 700A from eNB to UEs in the physical layer are calledphysical downlink shared channel (PDSCH) 702 and 711, and the datachannel transmitting data packet 700B from UEs to eNB in the physicallayer are called physical uplink shared channel (PUSCH) 704 and 705. Thecorresponding physical control channels, transmitted from eNB to UEs,indicate where the corresponding PDSCH 702 and 711 and/or PUSCH 704 and705 are in the frequency domain and in which manner the PDSCH 702 and711 and/or PUSCH 704 and 705 is transmitted, which are called physicaldownlink control channel (PDCCH) 702, 703, and 705. In FIG. 7, PDCCH 701may indicate the signaling for PDSCH 702 or PUSCH 704.

UEs measure the channel status, especially for multiple antennas.PMI/CQI/RI and other feedbacks may be based on the measurement ofreference signal. PMI is the precoding matrix indicator, CQI is thechannel quality indicator, and RI is the rank indicator of the precodingmatrix. There may be multiple reference signal resources configured fora UE. There is specific time-frequency resource and scrambling codeassigned by the eNB for each reference signal resource.

Usually, the eNBs may be arranged close to each other so that a decisionmade by a first eNB may have an impact on a second eNB. For example, theeNBs may use their transmit antenna arrays to form beams towards theirUEs when serving them. This may mean that if the first eNB decides toserve a first UE in a particular time-frequency resource, it may form abeam pointing to that UE. However, the pointed beam may extend into acoverage area of the second eNB and cause interference to UEs served bythe second eNB. The inter-cell interference (ICI) for small cellwireless communications systems is commonly referred to as aninterference limited cell scenario, which may be different from a noiselimited cell scenario seen in large cell wireless communicationssystems.

In an example embodiment, an eNodeB may control one or more cells.Multiple remote radio units may be connected to the same baseband unitof the eNodeB by fiber cable, and the latency between the baseband unitand the remote radio unit is quite small. Therefore the same basebandunit can process the coordinated transmission/reception of multiplecells. For example, the eNodeB may coordinate the transmissions ofmultiple cells to a UE, which is called coordinated multiple point(CoMP) transmission. The eNodeB may also coordinate the reception ofmultiple cells from a UE, which is called CoMP reception. In this case,the backhaul link between these cells with the same eNodeB is fastbackhaul and the scheduling of PDSCH transmitted in different cells forthe UE can be easily coordinated in the same eNodeB.

In an example embodiment, a device and method signaling a set ofdownlink analog beamforming reference signal (BFRS) to a UE is provided.A BFRS resource may include time, frequency and sequence. A BFRStransmission may consist of the sequential transmission of analogtransmit beams supported in the eNodeB. The cell signals the BFRSresource, its total number of analog beams, and the analog beam groupinginformation to the UE. The UE should not derive the digital CSI feedbackinvolving more than two analog beams from the same group.

In another example embodiment, a device and method for signaling a setof analog beam restriction configuration to UE are provided. Therestriction may indicate a set of analog beams upon which the UE shouldnot derive the digital CSI feedback including any of the analog beamsindicated in the restriction configuration. The UE should not derive thedigital CSI feedback involving more than two analog beams from the samegroup.

In an example embodiment, the signaling may be in the forms of macrocell broadcasting, macro sending UE-specific radio resource control(RRC) signaling, small cell broadcasting, small cells sendingUE-specific radio resource control (RRC) signaling, or any combinationof the above.

In an example embodiment, a UE receives the configuration of BFRStransmission of a set of network controllers and a set of analog beamrestriction configuration. The UE receives each transmit analog beamafter applying each of the UE's receive beams. The UE collects thechannel response for each of the transmit-receive-beam pairs. The UEperforms sorting and pruning on the transmit-receive-beam pairsaccording to some metric, e.g. reference signal received power (RSRP) orsignal-to-interference-plus-noise ratio (SINR).

In an example embodiment, a UE selects the best transmit-receive-beampairs to form the effective MIMO channels and virtual antenna ports.Multiple effective MIMO channels can be formed by including one transmitbeam from one or more transmit beam groups, or one or more receivebeams. For example, a system with four sets of transmit beams (one setof transmit beams includes the RF chain, phase shift, and antenna array)at the eNodeB side, and two sets of receive beams (one set of receivebeam includes RF chain, phase shift, and antenna array) at the UE side,could form 4×2, 3×2, 2×2, 1×2, 4×1, 3×1, 2×1 and 1×1 various effectiveMIMO channels.

The selection to form effective MIMO channels can follow the receivedanalog beam restriction configuration. The effective MIMO channel shouldnot include any transmit analog beams indicated in the restrictionconfiguration. The effective MIMO channel should not include more thanone transmit analog beam belonging to the same group.

In an example embodiment, the UE derives the CSI feedback based on theeffective MIMO channels and selects the best set(s) to feedback to thenetwork. The feedback set should include the indexes of the analogtransmit beams forming the selected effective MIMO channel and itscorresponding rank, CQI, PMI or the pre-coding matrix. More than one setof feedback may be reported to the network, covering different rank ordifferent effective MIMO choices of the same rank, according to networkfeedback configurations.

In an example embodiment, the UE only reports the best analog transmitbeams to the network. The reported transmit beams may not be from thesame group. The reported transmit beams may not include any transmitbeams indicated in the received beam restriction configuration. The UEmay send uplink sounding signals by applying the receive beams from theselected transmit-receive-beam pair as the transmit beams. The eNodeBreceives these analog beams and derives the CSI information for laterdownlink data transmission.

In an example embodiment, analog beams are divided into transmit groups.Each transmit group may correspond to one transmit RF chain. Eachtransmit group may contain many transmit beams, and when beam scanningis performed, each beam may be transmitted sequentially. The UE receivesthe beam scanning signal by sequentially trying each of the UE's receivebeams.

FIG. 8 is a diagram illustrating an example frame structure 800 inaccordance with an example embodiment. Here, the frame structure 800includes N wide beams (labeled 802A, 802B, 802N). Each wide beam 802A,802B, 802N includes K narrow beams within it (labeled 804A-K. 806A-K,and 808A-K.

Though the above descriptions are mainly for LTE systems, the conceptsmay be applicable in other systems such as HSPA systems, WiFi systems,etc.

FIG. 9 is a diagram illustrating a system 900 for sequentiallytransmitting a beam scanning signal in accordance with an exampleembodiment. On the transmit side 902, multiple RF transmitters 906A-906Dact to transmit the narrow beams sequentially to the receive side 904,where RF receivers 908A-908B sequentially try each of its receive beams.

The following figures are diagrams of a processing system that may beused for implementing the devices and methods disclosed herein. Specificdevices may utilize all of the components shown, or only a subset of thecomponents, and levels of integration may vary from device to device.

Certain embodiments are described herein as including logic or a numberof components, modules, or mechanisms. Modules may constitute eithersoftware modules (e.g., code embodied on a machine-readable medium) orhardware modules. A “hardware module” is a tangible unit capable ofperforming certain operations and may be configured or arranged in acertain physical manner. In various example embodiments, one or morecomputer systems (e.g., a standalone computer system, a client computersystem, or a server computer system) or one or more hardware modules ofa computer system (e.g., a processor or a group of processors) may beconfigured by software (e.g., an application or application portion) asa hardware module that operates to perform certain operations asdescribed herein.

In some embodiments, a hardware module may be implemented mechanically,electronically, or any suitable combination thereof. For example, ahardware module may include dedicated circuitry or logic that ispermanently configured to perform certain operations. For example, ahardware module may be a special-purpose processor, such as afield-programmable gate array (FPGA) or an application specificintegrated circuit (ASIC). A hardware module may also includeprogrammable logic or circuitry that is temporarily configured bysoftware to perform certain operations. For example, a hardware modulemay include software executed by a general-purpose processor or otherprogrammable processor. Once configured by such software, hardwaremodules become specific machines (or specific components of a machine)uniquely tailored to perform the configured functions and are no longergeneral-purpose processors. It will be appreciated that the decision toimplement a hardware module mechanically, in dedicated and permanentlyconfigured circuitry, or in temporarily configured circuitry (e.g.,configured by software) may be driven by cost and time considerations.

Accordingly, the phrase “hardware module” should be understood toencompass a tangible entity, be that an entity that is physicallyconstructed, permanently configured (e.g., hardwired), or temporarilyconfigured (e.g., programmed) to operate in a certain manner or toperform certain operations described herein. As used herein,“hardware-implemented module” refers to a hardware module. Consideringembodiments in which hardware modules are temporarily configured (e.g.,programmed), each of the hardware modules need not be configured orinstantiated at any one instance in time. For example, where a hardwaremodule comprises a general-purpose processor configured by software tobecome a special-purpose processor, the general-purpose processor may beconfigured as respectively different special-purpose processors (e.g.,comprising different hardware modules) at different times. Softwareaccordingly configures a particular processor or processors, forexample, to constitute a particular hardware module at one instance oftime and to constitute a different hardware module at a differentinstance of time.

Hardware modules can provide information to, and receive informationfrom, other hardware modules. Accordingly, the described hardwaremodules may be regarded as being communicatively coupled. Where multiplehardware modules exist contemporaneously, communications may be achievedthrough signal transmission (e.g., over appropriate circuits and buses)between or among two or more of the hardware modules. In embodiments inwhich multiple hardware modules are configured or instantiated atdifferent times, communications between such hardware modules may beachieved, for example, through the storage and retrieval of informationin memory structures to which the multiple hardware modules have access.For example, one hardware module may perform an operation and store theoutput of that operation in a memory device to which it iscommunicatively coupled. A further hardware module may then, at a latertime, access the memory device to retrieve and process the storedoutput. Hardware modules may also initiate communications with input oroutput devices, and can operate on a resource (e.g., a collection ofinformation).

The various operations of example methods described herein may beperformed, at least partially, by one or more processors that aretemporarily configured (e.g., by software) or permanently configured toperform the relevant operations. Whether temporarily or permanentlyconfigured, such processors may constitute processor-implemented modulesthat operate to perform one or more operations or functions describedherein. As used herein, “processor-implemented module” refers to ahardware module implemented using one or more processors.

Similarly, the methods described herein may be at least partiallyprocessor-implemented, with a particular processor or processors beingan example of hardware. For example, at least some of the operations ofa method may be performed by one or more processors orprocessor-implemented modules. Moreover, the one or more processors mayalso operate to support performance of the relevant operations in a“cloud computing” environment or as a “software as a service” (SaaS).For example, at least some of the operations may be performed by a groupof computers (as examples of machines including processors), with theseoperations being accessible via a network (e.g., the Internet) and viaone or more appropriate interfaces (e.g., an application programinterface (API)).

The performance of certain of the operations may be distributed amongthe processors, not only residing within a single machine, but deployedacross a number of machines. In some example embodiments, the processorsor processor-implemented modules may be located in a single geographiclocation (e.g., within a home environment, an office environment, or aserver farm). In other example embodiments, the processors orprocessor-implemented modules may be distributed across a number ofgeographic locations.

Machine and Software Architecture

The modules, methods, applications and so forth described in conjunctionwith FIGS. 1-9 are implemented, in some embodiments, in the context of amachine and an associated software architecture. The sections belowdescribe representative software architecture(s) and machine (e.g.,hardware) architecture(s) that are suitable for use with the disclosedembodiments.

Software architectures are used in conjunction with hardwarearchitectures to create devices and machines tailored to particularpurposes. For example, a particular hardware architecture coupled with aparticular software architecture will create a mobile device, such as amobile phone, tablet device, or so forth. A slightly different hardwareand software architecture may yield a smart device for use in the“internet of things” while yet another combination produces a servercomputer for use within a cloud computing architecture. Not allcombinations of such software and hardware architectures are presentedhere as those of skill in the art can readily understand how toimplement the inventive subject matter in different contexts from thedisclosure contained herein.

Software Architecture

FIG. 10 is a block diagram 1000 illustrating a representative softwarearchitecture 1002, which may be used in conjunction with varioushardware architectures herein described. FIG. 10 is merely anon-limiting example of a software architecture 1002 and it will beappreciated that many other architectures may be implemented tofacilitate the functionality described herein. The software architecture1002 may be executing on hardware such as machine 1100 of FIG. 11 thatincludes, among other things, processors 1110, memory/storage 1130, andI/O components 1150. A representative hardware layer 1004 is illustratedand can represent, for example, the machine 1100 of FIG. 11. Therepresentative hardware layer 1004 comprises one or more processingunits 1006 having associated executable instructions 1008. Executableinstructions 1008 represent the executable instructions of the softwarearchitecture 1002, including implementation of the methods, modules andso forth of FIGS. 1-9. Hardware layer 1004 also includes memory and/orstorage modules 1010, which also have executable instructions 1008.Hardware layer 1004 may also comprise other hardware 1012, whichrepresents any other hardware of the hardware layer 1004, such as theother hardware illustrated as part of machine 1100.

In the example architecture of FIG. 10, the software architecture 1002may be conceptualized as a stack of layers where each layer providesparticular functionality. For example, the software architecture 1002may include layers such as an operating system 1014, libraries 1016,frameworks/middleware 1018, applications 1020 and presentation layer1044. Operationally, the applications 1020 and/or other componentswithin the layers may invoke application programming interface (API)calls 1024 through the software stack and receive a response, returnedvalues, and so forth illustrated as messages 1026 in response to the APIcalls 1024. The layers illustrated are representative in nature and notall software architectures 1002 have all layers. For example, somemobile or special purpose operating systems may not provide aframeworks/middleware 1018, while others may provide such a layer. Othersoftware architectures may include additional or different layers.

The operating system 1014 may manage hardware resources and providecommon services. The operating system 1014 may include, for example, akernel 1028, services 1030, and drivers 1032. The kernel 1028 may act asan abstraction layer between the hardware and the other software layers.For example, the kernel 1028 may be responsible for memory management,processor management (e.g., scheduling), component management,networking, security settings, and so on. The services 1030 may provideother common services for the other software layers. The drivers 1032may be responsible for controlling or interfacing with the underlyinghardware. For instance, the drivers 1032 may include display drivers,camera drivers, Bluetooth® drivers, flash memory drivers, serialcommunication drivers (e.g., Universal Serial Bus (USB) drivers), Wi-Fi®drivers, audio drivers, power management drivers, and so forth,depending on the hardware configuration.

The libraries 1016 may provide a common infrastructure that may beutilized by the applications 1020 and/or other components and/or layers.The libraries 1016 typically provide functionality that allows othersoftware modules to perform tasks in an easier fashion than to interfacedirectly with the underlying operating system 1014 functionality (e.g.,kernel 1028, services 1030 and/or drivers 1032). The libraries 1016 mayinclude system libraries 1034 (e.g., C standard library) that mayprovide functions such as memory allocation functions, stringmanipulation functions, mathematic functions, and the like. In addition,the libraries 1016 may include API libraries 1036 such as medialibraries (e.g., libraries to support presentation and manipulation ofvarious media format such as MPEG4, H.264, MP3, AAC, AMR, JPG, PNG),graphics libraries (e.g., an OpenGL framework that may be used to render2D and 3D in a graphic content on a display), database libraries (e.g.,SQLite that may provide various relational database functions), weblibraries (e.g., WebKit that may provide web browsing functionality),and the like. The libraries 1016 may also include a wide variety ofother libraries 1038 to provide many other APIs to the applications 1020and other software components/modules.

The frameworks/middleware 1018 (also sometimes referred to asmiddleware) may provide a higher-level common infrastructure that may beutilized by the applications 1020 and/or other softwarecomponents/modules. For example, the frameworks/middleware 1018 mayprovide various graphic user interface (GUI) functions, high-levelresource management, high-level location services, and so forth. Theframeworks/middleware 1018 may provide a broad spectrum of other APIsthat may be utilized by the applications 1020 and/or other softwarecomponents/modules, some of which may be specific to a particularoperating system 1014 or platform.

The applications 1020 include built-in applications 1040 and/orthird-party applications 1042. Examples of representative built-inapplications 1040 may include, but are not limited to, a contactsapplication, a browser application, a book reader application, alocation application, a media application, a messaging application,and/or a game application. Third-party applications 1042 may include anyof the built-in applications 1040 as well as a broad assortment of otherapplications. In a specific example, the third-party application 1042(e.g., an application developed using the Android™ or iOS™ softwaredevelopment kit (SDK) by an entity other than the vendor of theparticular platform) may be mobile software running on a mobileoperating system such as iOS™, Android™, Windows® Phone, or other mobileoperating systems. In this example, the third-party application 1042 mayinvoke the API calls 1024 provided by the mobile operating system suchas operating system 1014 to facilitate functionality described herein.

The applications 1020 may utilize built-in operating system functions(e.g., kernel 1028, services 1030 and/or drivers 1032), libraries (e.g.,system libraries 1034, API libraries 1036, and other libraries 1038),and frameworks/middleware 1018 to create user interfaces to interactwith users of the system. Alternatively, or additionally, in somesystems, interactions with a user may occur through a presentationlayer, such as presentation layer 1044. In these systems, theapplication/module “logic” can be separated from the aspects of theapplication/module that interact with a user.

Some software architectures utilize virtual machines. In the example ofFIG. 10, this is illustrated by virtual machine 1048. A virtual machinecreates a software environment where applications/modules can execute asif they were executing on a hardware machine (such as the machine 1100of FIG. 11, for example). A virtual machine 1048 is hosted by a hostoperating system (operating system 1014 in FIG. 10) and typically,although not always, has a virtual machine monitor 1046, which managesthe operation of the virtual machine 1048 as well as the interface withthe host operating system (i.e., operating system 1014). A softwarearchitecture 1002 executes within the virtual machine 1048 such as anoperating system 1050, libraries 1052, frameworks/middleware 1054,applications 1056 and/or presentation layer 1058. These layers ofsoftware architecture executing within the virtual machine 1048 can bethe same as corresponding layers previously described or may bedifferent.

Example Machine Architecture and Machine-Readable Medium

FIG. 11 is a block diagram illustrating components of a machine 1100,according to some example embodiments, able to read instructions 1116from a machine-readable medium (e.g., a machine-readable storage medium)and perform any one or more of the methodologies discussed herein.Specifically, FIG. 11 shows a diagrammatic representation of the machine1100 in the example form of a computer system, within which instructions1116 (e.g., software, a program, an application, an applet, an app, orother executable code) for causing the machine 1100 to perform any oneor more of the methodologies discussed herein may be executed. Forexample, the instructions 1116 may cause the machine 1100 to execute theflow diagrams of FIGS. 4 and 5. Additionally, or alternatively, theinstructions 1116 may implement modules of FIGS. 1-9, and so forth. Theinstructions 1116 transform the general, non-programmed machine 1100into a particular machine programmed to carry out the described andillustrated functions in the manner described. In alternativeembodiments, the machine 1100 operates as a standalone device or may becoupled (e.g., networked) to other machines. In a networked deployment,the machine 1100 may operate in the capacity of a server machine or aclient machine in a server-client network environment, or as a peermachine in a peer-to-peer (or distributed) network environment. Themachine 1100 may comprise, but not be limited to, a server computer, aclient computer, a personal computer (PC), a tablet computer, a laptopcomputer, a netbook, a set-top box (STB), a personal digital assistant(PDA), an entertainment media system, a cellular telephone, a smartphone, a mobile device, a wearable device (e.g., a smart watch), a smarthome device (e.g., a smart appliance), other smart devices, a webappliance, a network router, a network switch, a network bridge, or anymachine capable of executing the instructions 1116, sequentially orotherwise, that specify actions to be taken by machine 1100. Further,while only a single machine 1100 is illustrated, the term “machine”shall also be taken to include a collection of machines 1100 thatindividually or jointly execute the instructions 1116 to perform any oneor more of the methodologies discussed herein.

The machine 1100 may include processors 1110, memory/storage 1130, andI/O components 1150, which may be configured to communicate with eachother such as via a bus 1102. In an example embodiment, the processors1110 (e.g., a central processing unit (CPU), a reduced instruction setcomputing (RISC) processor, a complex instruction set computing (CISC)processor, a graphics processing unit (GPU), a digital signal processor(DSP), an application specific integrated circuit (ASIC), aradio-frequency integrated circuit (RFIC), another processor, or anysuitable combination thereof) may include, for example, processor 1112and processor 1114 that may execute instructions 1116. The term“processor” is intended to include multi-core processor 1112, 1114 thatmay comprise two or more independent processors 1112, 1114 (sometimesreferred to as “cores”) that may execute instructions 1116contemporaneously. Although FIG. 11 shows multiple processors 1110, themachine 1100 may include a single processor 1112, 1114 with a singlecore, a single processor 1112, 1114 with multiple cores (e.g., amulti-core processor 1112, 1114), multiple processors 1112, 1114 with asingle core, multiple processors 1112, 1114 with multiples cores, or anycombination thereof.

The memory/storage 1130 may include a memory 1132, such as a mainmemory, or other memory storage, and a storage unit 1136, bothaccessible to the processors 1110 such as via the bus 1102. The storageunit 1136 and memory 1132 store the instructions 1116 embodying any oneor more of the methodologies or functions described herein. Theinstructions 1116 may also reside, completely or partially, within atleast one of the processors 1110 (e.g., within the processor 1112,1114's cache memory), or any suitable combination thereof, duringexecution thereof by the machine 1100. Accordingly, the memory 1132, thestorage unit 1136, and the memory of processors 1110 are examples ofmachine-readable media.

As used herein, “machine-readable medium” means a device able to storeinstructions 1116 and data temporarily or permanently and may include,but is not be limited to, random-access memory (RAM), read-only memory(ROM), buffer memory, flash memory, optical media, magnetic media, cachememory, other types of storage (e.g., erasable programmable read-onlymemory (EEPROM)) and/or any suitable combination thereof. The term“machine-readable medium” should be taken to include a single medium ormultiple media (e.g., a centralized or distributed database, orassociated caches and servers) able to store instructions 1116. The term“machine-readable medium” shall also be taken to include any medium, orcombination of multiple media, that is capable of storing instructions(e.g., instructions 1116) for execution by a machine (e.g., machine1100), such that the instructions 1116, when executed by one or moreprocessors of the machine 1100 (e.g., processors 1110), cause themachine 1100 to perform any one or more of the methodologies describedherein. Accordingly, a “machine-readable medium” refers to a singlestorage apparatus or device, as well as “cloud-based” storage systems orstorage networks that include multiple storage apparatus or devices. Theterm “machine-readable medium” excludes signals per se.

The I/O components 1150 may include a wide variety of components toreceive input, provide output, produce output, transmit information,exchange information, capture measurements, and so on. The specific I/Ocomponents 1150 that are included in a particular machine 1100 willdepend on the type of machine 1100. For example, portable machines suchas mobile phones will likely include a touch input device or other suchinput mechanisms, while a headless server machine will likely notinclude such a touch input device. It will be appreciated that the I/Ocomponents 1150 may include many other components that are not shown inFIG. 11. The I/O components 1150 are grouped according to functionalitymerely for simplifying the following discussion and the grouping is inno way limiting. In various example embodiments, the I/O components 1150may include output components 1152 and input components 1154. The outputcomponents 1152 may include visual components (e.g., a display such as aplasma display panel (PDP), a light emitting diode (LED) display, aliquid crystal display (LCD), a projector, or a cathode ray tube (CRT)),acoustic components (e.g., speakers), haptic components (e.g., avibratory motor, resistance mechanisms), other signal generators, and soforth. The input components 1154 may include alphanumeric inputcomponents (e.g., a keyboard, a touch screen configured to receivealphanumeric input, a photo-optical keyboard, or other alphanumericinput components), point based input components (e.g., a mouse, atouchpad, a trackball, a joystick, a motion sensor, or other pointinginstrument), tactile input components (e.g., a physical button, a touchscreen that provides location and/or force of touches or touch gestures,or other tactile input components), audio input components (e.g., amicrophone), and the like.

In further example embodiments, the I/O components 1150 may includebiometric components 1156, motion components 1158, environmentalcomponents 1160, or position components 1162 among a wide array of othercomponents. For example, the biometric components 1156 may includecomponents to detect expressions (e.g., hand expressions, facialexpressions, vocal expressions, body gestures, or eye tracking), measurebiosignals (e.g., blood pressure, heart rate, body temperature,perspiration, or brain waves), identify a person (e.g., voiceidentification, retinal identification, facial identification,fingerprint identification, or electroencephalogram basedidentification), and the like. The motion components 1158 may includeacceleration sensor components (e.g., accelerometer), gravitation sensorcomponents, rotation sensor components (e.g., gyroscope), and so forth.The environmental components 1160 may include, for example, illuminationsensor components (e.g., photometer), temperature sensor components(e.g., one or more thermometer that detect ambient temperature),humidity sensor components, pressure sensor components (e.g.,barometer), acoustic sensor components (e.g., one or more microphonesthat detect background noise), proximity sensor components (e.g.,infrared sensors that detect nearby objects), gas sensors (e.g., gasdetection sensors to detection concentrations of hazardous gases forsafety or to measure pollutants in the atmosphere), or other componentsthat may provide indications, measurements, or signals corresponding toa surrounding physical environment. The position components 1162 mayinclude location sensor components (e.g., a Global Position System (GPS)receiver component), altitude sensor components (e.g., altimeters orbarometers that detect air pressure from which altitude may be derived),orientation sensor components (e.g., magnetometers), and the like.

Communication may be implemented using a wide variety of technologies.The I/O components 1150 may include communication components 1164operable to couple the machine 1100 to a network 1180 or devices 1170via coupling 1182 and coupling 1172 respectively. For example, thecommunication components 1164 may include a network interface componentor other suitable device to interface with the network 1180. In furtherexamples, communication components 1164 may include wired communicationcomponents, wireless communication components, cellular communicationcomponents, near field communication (NFC) components, Bluetooth®components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and othercommunication components to provide communication via other modalities.The devices 1170 may be another machine or any of a wide variety ofperipheral devices (e.g., a peripheral device coupled via a UniversalSerial Bus (USB)).

Moreover, the communication components 1164 may detect identifiers orinclude components operable to detect identifiers. For example, thecommunication components 1164 may include radio frequency identification(RFID) tag reader components, NFC smart tag detection components,optical reader components (e.g., an optical sensor to detectone-dimensional bar codes such as Universal Product Code (UPC) bar code,multi-dimensional bar codes such as Quick Response (QR) code, Azteccode, Data Matrix, Dataglyph, MaxiCode, PDF417, Ultra Code, UCC RSS-2Dbar code, and other optical codes), or acoustic detection components(e.g., microphones to identify tagged audio signals). In addition, avariety of information may be derived via the communication components1164, such as location via Internet Protocol (IP) geo-location, locationvia Wi-Fi® signal triangulation, location via detecting a NFC beaconsignal that may indicate a particular location, and so forth.

Transmission Medium

In various example embodiments, one or more portions of the network 1180may be an ad hoc network, an intranet, an extranet, a virtual privatenetwork (VPN), a local area network (LAN), a wireless LAN (WLAN), a widearea network (WAN), a wireless WAN (WWAN), a metropolitan area network(MAN), the Internet, a portion of the Internet, a portion of the publicswitched telephone network (PSTN), a plain old telephone service (POTS)network, a cellular telephone network, a wireless network, a Wi-Fi®network, another type of network, or a combination of two or more suchnetworks. For example, the network 1180 or a portion of the network 1180may include a wireless or cellular network and the coupling 1182 may bea Code Division Multiple Access (CDMA) connection, a Global System forMobile communications (GSM) connection, or other type of cellular orwireless coupling. In this example, the coupling 1182 may implement anyof a variety of types of data transfer technology, such as SingleCarrier Radio Transmission Technology (1×RTT), Evolution-Data Optimized(EVDO) technology, General Packet Radio Service (GPRS) technology,Enhanced Data rates for GSM Evolution (EDGE) technology, thirdGeneration Partnership Project (3GPP) including 3G, fourth generationwireless (4G) networks, Universal Mobile Telecommunications System(UMTS), High Speed Packet Access (HSPA), Worldwide Interoperability forMicrowave Access (WiMAX), Long Term Evolution (LTE) standard, othersdefined by various standard setting organizations, other long rangeprotocols, or other data transfer technology.

The instructions 1116 may be transmitted or received over the network1180 using a transmission medium via a network interface device (e.g., anetwork interface component included in the communication components1164) and utilizing any one of a number of well-known transfer protocols(e.g., hypertext transfer protocol (HTTP)). Similarly, the instructions1116 may be transmitted or received using a transmission medium via thecoupling 1192 (e.g., a peer-to-peer coupling) to devices 1170. The term“transmission medium” shall be taken to include any intangible mediumthat is capable of storing, encoding, or carrying instructions 1116 forexecution by the machine 1100, and includes digital or analogcommunications signals or other intangible medium to facilitatecommunication of such software.

Language

Throughout this specification, plural instances may implementcomponents, operations, or structures described as a single instance.Although individual operations of one or more methods are illustratedand described as separate operations, one or more of the individualoperations may be performed concurrently, and nothing requires that theoperations be performed in the order illustrated. Structures andfunctionality presented as separate components in example configurationsmay be implemented as a combined structure or component. Similarly,structures and functionality presented as a single component may beimplemented as separate components. These and other variations,modifications, additions, and improvements fall within the scope of thesubject matter herein.

Although an overview of the inventive subject matter has been describedwith reference to specific example embodiments, various modificationsand changes may be made to these embodiments without departing from thebroader scope of embodiments of the present disclosure. Such embodimentsof the inventive subject matter may be referred to herein, individuallyor collectively, by the term “invention” merely for convenience andwithout intending to voluntarily limit the scope of this application toany single disclosure or inventive concept if more than one is, in fact,disclosed.

The embodiments illustrated herein are described in sufficient detail toenable those skilled in the art to practice the teachings disclosed.Other embodiments may be used and derived therefrom, such thatstructural and logical substitutions and changes may be made withoutdeparting from the scope of this disclosure. The Detailed Description,therefore, is not to be taken in a limiting sense, and the scope ofvarious embodiments is defined only by the appended claims, along withthe full range of equivalents to which such claims are entitled.

As used herein, the term “or” may be construed in either an inclusive orexclusive sense. Moreover, plural instances may be provided forresources, operations, or structures described herein as a singleinstance. Additionally, boundaries between various resources,operations, modules, engines, and data stores are somewhat arbitrary,and particular operations are illustrated in a context of specificillustrative configurations. Other allocations of functionality areenvisioned and may fall within a scope of various embodiments of thepresent disclosure. In general, structures and functionality presentedas separate resources in the example configurations may be implementedas a combined structure or resource. Similarly, structures andfunctionality presented as a single resource may be implemented asseparate resources. These and other variations, modifications,additions, and improvements fall within a scope of embodiments of thepresent disclosure as represented by the appended claims. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense.

1. A method for wireless communications, the method comprising:receiving, by a user equipment (UE) from a first network controller, aconfiguration of analog transmit beams for a beamforming referencesignal (BFRS) and an analog beam selection restriction configuration forrestricting generation of digital channel state information (CSI)feedback; receiving, by the UE from the first network controller, theBFRS; generating, by the UE, CSI feedback of the BFRS according to theconfiguration of analog transmit beams for the BFRS and the analog beamselection restriction configuration for restricting the generation ofthe digital CSI feedback, and transmitting, by the UE to the firstnetwork controller, the CSI feedback.
 2. The method according to claim1, further comprising: determining, by the UE, one or more digitalmultiple-input and multiple-output (MIMO) channels in accordance with aquantity of the analog transmit beams and the analog beam selectionrestriction configuration, each digital MIMO channel being derived on afirst analog transmit beam different from a second analog transmit beamindicated by the analog beam selection restriction configuration; andderiving, by the UE, digital CSI feedback based on the one or moredigital MIMO channels.
 3. The method according to claim 1, wherein theanalog beam selection restriction configuration indicates one or moreanalog beams not to be used by the UE to derive the digital CSIfeedback.
 4. The method according to claim 1, further comprising:receiving, by the UE from the first network controller, analog beamgrouping information for the analog transmit beams, the analog beamselection restriction configuration indicating that UE should not derivedigital CSI feedback involving more than two analog beams from a samegroup of analog beams.
 5. The method according to claim 1, furthercomprising: receiving, by the UE from the first network controller,analog beam grouping information for the analog transmit beams, whereinthe CSI feedback comprises digital CSI feedback involving no more thantwo analog beams from a same group of analog beams.
 6. A user equipment(UE), the UE comprising: a transmitter, a receiver, a non-transitorymemory storage comprising instructions; and one or more processors incommunication with the transmitter, the receiver and the non-transitorymemory, wherein the one or more processors execute the instructions to:receive, via the receiver, a configuration of analog transmit beams fora beamforming reference signal (BFRS) and an analog beam selectionrestriction configuration for restricting generation of a digitalchannel state information (CSI) feedback; receive, via the receiver, theBFRS on radio transmission resources; generate a CSI feedback of theBFRS according to the configuration of analog transmit beams for theBFRS and the analog beam selection restriction configuration forrestricting the generation of the digital CSI feedback; and transmit,via the transmitter, the CSI feedback.
 7. The UE according to claim 6,wherein the one or more processors are further configured to: determineone or more digital multiple-input and multiple-output (MIMO) channelsin accordance with a quantity of the analog transmit beams and theanalog beam selection restriction configuration, each digital MIMOchannel being derived on a first analog transmit beam different from asecond analog transmit beam indicated by the analog beam selectionrestriction configuration; and deriving, by the UE, digital CSI feedbackbased on the one or more digital MIMO channels.
 8. The UE according toclaim 6, wherein the analog beam selection restriction configurationindicates one or more analog beams not to be used by the UE to derivethe digital CSI feedback.
 9. The UE according to claim 6, wherein theone or more processors are further configured to: receive analog beamgrouping information for the analog transmit beams, the analog beamselection restriction configuration indicating that the UE should notderive digital CSI feedback involving more than two analog beams from asame group of analog beams.
 10. The UE according to claim 6, wherein theone or more processors are further configured to: receive analog beamgrouping information for the analog transmit beams, the CSI feedbackcomprising digital CSI feedback involving no more than two analog beamsfrom a same group of analog beams.
 11. A method for wirelesscommunications, the method comprising: signaling, by a first networkcontroller to a user equipment (UE), a configuration of analog transmitbeams for a beamforming reference signal (BFRS) and an analog beamselection restriction configuration for restricting generation ofdigital channel state information (CSI) feedback; transmitting, by thefirst network controller to the UE, the BFRS using radio transmissionresources; and receiving, by the first network controller from the UE,CSI feedback generated according to the configuration of analog transmitbeams for the BFRS and the analog beam selection restrictionconfiguration.
 12. The method according to claim 11, further comprising:receiving, by the first network controller, information of a transmitbeam selected by the UE; receiving, by the first network controllerusing the transmit beam as a receive beam, signals from the UE; andderiving, by the first network controller, baseband CSI in accordancewith the received signals.
 13. The method according to claim 11, whereinthe analog beam selection restriction configuration indicates one ormore analog beams not to be used by the UE to derive the digital CSIfeedback.
 14. The method according to claim 11, further comprising:transmitting, by the first network controller to the UE, analog beamgrouping information for the analog transmit beams, the analog beamselection restriction configuration indicating that the UE should notderive digital CSI feedback involving more than two analog beams from asame group of analog beams.
 15. The method according to claim 11,further comprising: transmitting, by the first network controller to theUE, analog beam grouping information for the analog transmit beams,wherein the CSI feedback comprises digital CSI feedback including nomore than two analog beams from a same group of analog beams.
 16. Anetwork controller comprising: a transmitter, a receiver, anon-transitory memory storage comprising instructions; and one or moreprocessors in communication with the transmitter, the receiver and thenon-transitory memory, wherein the instructions, upon execution by theone or more processors, cause the network controller to: signal aconfiguration of analog transmit beams for a beamforming referencesignal (BFRS) and an analog beam selection restriction configuration forrestricting generation of digital channel state information (CSI)feedback; transmit the BFRS; and receive CSI feedback generatedaccording to the configuration of analog transmit beams for the BFRS andthe analog beam selection restriction configuration.
 17. The networkcontroller according to claim 16, wherein execution of the instructionsby the one or more processors cause the network controller to: receiveinformation of a transmit beam selected by the UE; receive signals fromthe UE using the transmit beam as a receive beam; and derive basebandCSI in accordance with the received signals.
 18. The network controlleraccording to claim 16, wherein the analog beam selection restrictionconfiguration indicates one or more analog beams not to be used by theUE to derive the digital CSI feedback.
 19. The network controlleraccording to claim 16, wherein execution of the instructions by the oneor more processors cause the network controller to: transmit analog beamgrouping information for the analog transmit beams, the analog beamselection restriction configuration indicating that the UE should notderive a digital CSI feedback involving more than two analog beams froma same group of analog beams.
 20. The network controller according toclaim 16, wherein execution of the instructions by the one or moreprocessors cause the network controller to: transmit analog beamgrouping information for the analog transmit beams, the CSI feedbackcomprising digital CSI feedback involving no more than two analog beamsfrom a same group of analog beams.